   [{:$project
     (reduce
      (fn [project label]
-       (assoc project label (str "$_history." label)))
+       (assoc project label (str "$_history." (name label))))
      {} labels)}])
 
 (defn limit

   [protograph.kafka :as kafka]
   [ophion.config :as config]
   [ophion.mongo :as mongo]))

(defn where
  [where]

  [{:$project
    (reduce
     (fn [project value]
       (assoc project value (dollar value)))
     {} values)}])

(defn mark
